rijndael() can be used to store data you need to decrypt later, like the
contents of cookies. It should never be used to store passwords.
Instead you should use the one way hashing methods provided by
hash()

When comparing values hashed with bcrypt, the original hash should be
provided as the $salt parameter. This allows bcrypt to reuse the same
cost and salt values, allowing the generated hash to return the same
resulting hash, given the same input value.